Spring

Abstract

Disclosed is a spring formed from a synthetic resin into one body, including: a plurality of annular members arranged in such a manner as to be coaxial with each other and spaced in parallel to each other; and elastic linkage members for linking the annular members to each other at a plurality of points. In the spring, each of the elastic linkage members is arranged along a virtual cylindrical face formed by the annular members and formed into a lying U-shape curved in the peripheral direction of the annular members; radii of adjacent ones of the annular members are different from each other; and one end portion and the other end portion of each of the elastic linkage members, which portions are respectively linked to the adjacent ones of the annular members, are not overlapped to each other in the axial direction. These springs are locked integrally with a pair of upper and lower network plane members, which members include over the surfaces thereof locking members for locking upper and lower ends of the springs respectively, in such a manner as to be held therebetween, to form a spring assembly for a mattress.

What is claimed is: 
     
       1. A spring formed from a synthetic resin comprising: a plurality of annular members arranged coaxially and spaced from each other in an axial direction, wherein adjacent ones of the annular members have different radii; and   a plurality of elongated elastic linkage members having a U-shape extending in a peripheral direction when viewed in a radial direction defined by the annular members, the linkage members being disposed between two adjacent annular members and connected thereto at two ends of the U shape.   
     
     
       2. The spring of claim 1, wherein at least one of the annular members has cutout portions that overlap with a curved portion of the U shape of the linkage members when viewed along the axial direction. 
     
     
       3. The spring of claim 2, wherein two connection points of each linkage member on the two adjacent annular members are offset from each other in the peripheral direction when viewed along the axial direction such that one straight portion of the U-shaped linkage member is longer than another straight portion, and wherein the cutout portions are provided on the annular member that is connected to the longer one of the straight portions of the linkage members. 
     
     
       4. The spring of any one of claims 1 to 3, wherein at least one of the annular member is connected to linkage members on both sides, the at least one annular member having at least one restriction plate protruding from an outer or inner peripheral, the restriction plate being disposed between linkage members on both sides of the annular member when the spring is depressed. 
     
     
       5. A spring assembly comprising: a plurality of springs according to claim 1,   an upper and a lower network plane member each having locking members provided on their surfaces for respectively locking two outermost annular members of each spring to hold the spring between the upper and lower network plane members.   
     
     
       6. The spring assembly of claim 5, wherein the upper and lower network plane members are formed of a plurality of annular bodies joined to each other, the annular bodies having a shape corresponding to the outermost annular members of the springs, wherein the locking members are provided on the annular bodies and spaced in a peripheral direction. 
     
     
       7. The spring assembly of claim 5, wherein the locking members on the upper network plane are offset in the peripheral direction from the locking members on the lower network plane when viewed along the axial direction.